This invention relates to the method and apparatus for accumulating individual incoming planar tray-like objects into a stack, or for individually dispensing said objects from a preaccumulated stack.
There are many instances in the prior art when it has been found desirable to accumulate planar objects into a stack, as for packaging and shipping the objects. In other operations it is found desirable to dispense individual planar objects from a preformed stack. As one example, U.S. Pat. No. 3,233,891 might be cited. This apparatus is for accumulating individual sheets of plywood as they depart from a conveyor belt into packages of predetermined size for subsequent banding and shipping. This device had to deal with the problem of continuing to form these unit-sized stacks as the sheets continued in uninterrupted fashion from the conveyor line.
In many cases stacking or unstacking of planar or tray-like units has been done manually. An instance of this is in plant nurseries where potted plants of various types are grown for sale. The pots are contained in the greenhouses on large trays or tables, roughly five by ten feet in outside dimensions. These trays or tables have rollers on the bottom and are handled within the greenhouse by a transport means which normally comprises a set of rails. After the plants have grown to the appropriate size and are ready for sale, the trays or tables are handled as a unit and rolled along the transport system to the shipping area of the nursery. Here the potted plants are removed and otherwise packaged for shipping. The empty tables or trays are normally cleaned and stacked by hand. These stacks are then transported by truck or other means to the receiving end of the greenhouse where newly potted plants are placed on them for growth. While these trays are not heavy, because of their large dimensions they are awkward and require at least two people for handling. This creates the problem of increased labor costs in an industry which is fiercely competitive and often of low profitability. Many other materials-handling situations in which objects are transported on tray-like surfaces which must ultimately be returned to a point of origin could be cited with equal ease.